A white Christmas will be a U.S. rarity in 2011; November the globe's 12th warmest

A white Christmas will be a rarity across most of the U.S. this year, as December temperatures have been more typical of November, and very little snow has fallen. Large portions of the eastern half of the country have been more than 4°F above average so far in December, with temperatures averaging 8°F above average over portions of North Dakota.This is quite a switch from the previous two winters, which were both much colder and snowier than average. All three winters featured La Niña conditions in the Eastern Pacific Ocean, so that cannot explain the difference. A key reason for the December warmth this year and the cold and snowy Decembers of 2010 and 2009 is a weather pattern known as the Arctic Oscillation.

Figure 1. Departure of temperature from average over the 30-day period ending on December 22, 2011. Image credit: NOAA/CPC.

Figure 2. Top: snow depth measured in the U.S. on December 22, 2011, after a month with a strong positive phase of the Arctic Oscillation (AO). Bottom: Snow depth measured in the U.S. on December 22, 2010, after a month with a strong negative phase of the Arctic Oscillation (AO). Image credit: NOAA/NOHRSC.

The Arctic Oscillation and its influence on winter weatherThe Arctic Oscillation (AO), and its close cousin, the North Atlantic Oscillation (NAO), are climate patterns in the Northern Hemisphere defined by fluctuations in the difference of sea-level pressure between the Icelandic Low and the Azores High. It is one of oldest known climate oscillations--seafaring Scandinavians described the pattern several centuries ago. Through east-west oscillation motions of the Icelandic Low and the Azores High, the AO and NAO control the strength and direction of westerly winds and storm tracks across the North Atlantic. A large difference in the pressure between Iceland and the Azores (positive AO/NAO) leads to increased westerly winds and mild winter in the U.S. and Western Europe. Positive AO/NAO conditions also cause the Icelandic Low to draw a stronger south-westerly flow of air over eastern North America, preventing Arctic air from plunging southward. In contrast, if the difference in sea-level pressure between Iceland and the Azores is small (negative AO/NAO), westerly winds are suppressed, allowing Arctic air to spill southwards into eastern North America more readily. Negative AO/NAO winters tend to bring cold winters to Europe and the U.S. East Coast, but leads to very warm conditions in the Arctic, since all the cold air spilling out of the Arctic gets replaced by warm air flowing poleward. The winter of 2009 - 2010 had the most extreme negative NAO and AO since record keeping began in 1865; a very extreme AO/NAO also developed during the winter of 2010 - 2011. But this year, the pattern has flipped. The AO has been almost as strong, but in the opposite sense--a positive AO, leading to very warm conditions over the U.S. Unfortunately, the AO is difficult to predict more than a week or two and advance, and we don't understand why the AO can vary so much from winter to winter. The latest predictions from the ECMWF and GFS models show this positive AO pattern continuing for at least the next ten days. Real winter conditions won't arrive in the U.S. until the first week of January, at the earliest. Between now and the end of 2011, the only major winter storm the GFS model expects in the U.S. will be in the Pacific Northwest, on December 30 - 31.

Figure 3. The departure of temperature from average in Centigrade during the November - December - January period during various phases of the Arctic Oscillation (AO). Positive AO conditions lead to warm winters in the U.S., while negative AO conditions lead to cold winters. Image credit: NOAA/CPC.

A warm November for the U.S. In the contiguous U.S., November ranked as the 25th warmest November in the 117-year record. Thirteen states in the Northeast and Upper Midwest recorded a top-ten warmest November, and no states had a top-ten coldest November. Eight states had a top-ten wettest November--Indiana, Ohio, Missouri,Illinois, Kentucky, Tennessee, Arkansas, and Oklahoma. One state had a top-ten driest month, Minnesota. Texas had its 39th driest November on record, keeping 76% of Texas under extreme to exceptional drought as of December 13, according to the U.S. Drought Monitor.

A weak La Niña continuesA borderline weak/moderate La Niña event continues in the equatorial Pacific, where sea surface temperatures were approximately 1.0°C below average during the first half of December. The impacts of a La Niña on U.S. weather are well-defined. It is likely that the drought in the South, especially Texas, will continue, along with above average temperatures. The Northwest can expect cooler than average temperatures, as well as the potential for another winter with a heavy snowpack across the western United States.

Arctic sea ice extent third lowest on recordArctic sea ice extent was at its third lowest on record in November, behind 2006 and 2010, according to the National Snow and Ice Data Center. Sea ice records date back to 1979.

Donations sought for the East Africa famineWeather Underground has partnered with the International Rescue Committee (IRC) to help the Horn of Africa region during the ongoing famine. With the help of the Weather Underground community, we hope to raise $10,000 that will go toward helping the refugees survive the crisis. Weather Underground will match the community's donation dollar-for-dollar up to $10,000 for a total donation of $20,000. Please visit the East Africa famine donation page to help out. Ninety cents of every dollar donated goes directly to the people in need.

Just imagine yourself being interviewed for a company doing business in LAmerica and getting the position.... because of your ability to comunicate.... Learn to master Spanish.... Ahh, Include also Mandarin....

Those are images from space, hydrus. Not weather satellites but, nice images regardless. It is kinda like taking your first look in a mirror. Sadly, for me, my first look was much better than my last look. sigh .... who IS that old man?!?!?!

I said in my post that the image was taken from a rocket..Post# 56 is the TIROS-1 satellite image.. Did you forget to take your Geritol today Rook?..jk...really..jk.:)

The Nighttime Lights of the World data set is compiled from the October 1994 - March 1995 nighttime data collected when moonlight was low. Using the Operational Linescan System (OLS) thermal infrared band, areas containing clouds were removed and the remaining area used in the time series. This image is actually a composite of hundreds of pictures acquired by three of the four DMSP satellites, which operate in low-altitude polar orbits and have the unique capability to detect low levels of visible-near infrared (VNIR) radiance at night.http://upload.wikimedia.org/wikipedia/common s/6/61/Flat_earth_night.png

Quoting hydrus:The first images from space were taken on the sub-orbital V-2 rocket flight launched by the U.S. on October 24, 1946.

Those are images from space, hydrus. Not weather satellites but, nice images regardless. It is kinda like taking your first look in a mirror. Sadly, for me, my first look was much better than my last look. sigh .... who IS that old man?!?!?!

Said I, to the Bishop of Charleston: "The Diocese oughta offer Spanish lessons free of charge to people active in parishes with high numbers of Spanish speaking parishioners...in order that we may build stronger relationships."

Said he to me: "That's a fine damned idea! And I appoint you in charge of making that happen! And be sure to enroll yourself as the first student!"

So...I'm sorta stuck....

Good luck its boring or that could be my teacher i dont know, i hate when people screw you over like that

Said I, to the Bishop of Charleston: "The Diocese oughta offer Spanish lessons free of charge to people active in parishes with high numbers of Spanish speaking parishioners...in order that we may build stronger relationships."

Said he to me: "That's a fine damned idea! And I appoint you in charge of making that happen! And be sure to enroll yourself as the first student!"

Notice also that Jeff Masters uses 1971-2000 averages as comparison. Everyone knows the 1970's were colder then the previously 100 year averages, but it makes for a more impressive comparison for him.

From the source:"Temperature anomalies for November 2011, September–November 2011, and January–November are shown on the dot maps in the following section. The dot maps on the left provide a spatial representation of anomalies calculated from the Global Historical Climatology Network (GHCN) dataset of land surface stations using a 1961–1990 base period. The dot maps on the right are a product of a merged land surface and sea surface temperature (SST) anomaly analysis developed by Smith et al. (2008). For the merged land surface and SST analysis, temperature anomalies with respect to the 1971–2000 average for land and ocean are analyzed separately and then merged to form the global analysis. For more information, please visit NCDC's Global Surface Temperature Anomalies page."

Also: "The maps show temperature anomalies relative to the 1971-2000 base period. This period is used because it has the widest distribution for historical data, which enables more resolution (detail) for comparing region-by-region effects."

Quoting StormTracker2K:With such an extreme drought in Texas I wonder how they are not having such an extreme water shortage?

It is still pretty bad here as far as not using water, i cannot wash my car, no sprinklers etc. Unfortunately the Highland Lakes west of Austin are just as dry as they were 6 months ago because the rains have been in the eastern half of the state, so the lakes are still 60 to 70 percent dry. I hope they are Wrong about a Warm and Dry winter for Texas, we get enough warm days the rest of the year, i enjoy the few cold days we get here. Happy Holidays to all from Texas

Quoting 12george1:I don't get it, if there is too much snow, it is because of global warming and if there is not very much snow, it is also because of global warming.

Quoting BahaHurican:U're not getting it because u don't yet grasp that too much snow [for u] means not enough snow somewhere else. The warming of the atmosphere is influencing weather patterns by intensifying their effects as well as by shifting the patterns themselves. It'slike a scale; if one side goes up, it's because the other side went down.

The global part is really meant to mean "impacts the whole world".

Quoting weatherh98:Why do some ares get colder whileothrs get warmer??

When global temperatures are warm, the Arctic sea ice melts to unusually low minima, causing winter extremes in the Arctic oscillation. Often, this also sets up an Arctic dipole, when both the AO and the NAO are in phase. The AO frequently creates both temperature and precipitation extremes across the US.

In general, precipitation shifts and extremes will likely increase given factors related to contemporary climate change. Evaporation increases, and this inevitably leads to increases in both floods and droughts, and sometimes in the same place: arable land. This is likely to increase food prices as well, in addition to global protests and uprisings sweeping the planet. Additionally, the natural oscillations such as ENSO, the Arctic anomalies and others, will likely increase in amplitude. A shift from the norm will incur more deviations. In general, climate in terms of temperatures may see a dampening in long-term temperature oscillations caused by solar and oceanic cycles, but extreme swings in weather conditions are likely to increase and persist.